This invention relates to a hipbone endoprosthesis comprising an endomedullar infibulum made of a metal material which can be inserted into the medullar channel of the femur following removal of the femur epiphysis, and a spherical head made of a ceramic material which is associable with that portion of said infibulum protruding from the medullar channel.
With the adoption of ceramic materials for the spherical head construction, some considerable problems arise in connection with the rigid coupling of the infibulum to the spherical head. That coupling is in fact obtained by forming in the spherical head a frustoconical seat, wherein a complemantary portion of the infibulum is force fitted. The seat is individually formed in the spherical head, and a high degree of precision is required in its formation if an incorrect distribution of the loads is to be avoided which might result in the ceramic head being cracked, either while assembling the infibulum or during the prosthesis use, in view of the low tensile strength of ceramic materials.